1. Field of the Invention
The present invention relates generally to transferring wafers among modules of semiconductor processing equipment, and more particularly to nesting certain modules of the equipment, and methods of implementing such nesting, to facilitate transfer of wafers among separate chambers of semiconductor processing equipment while reducing the area footprint occupied by the equipment.
2. Description of the Related Art
In the manufacture of semiconductor devices, process chambers are interfaced to permit transfer of wafers or substrates, for example, between the interfaced chambers. Such transfer is via transport modules that move the wafers, for example, through slots or ports that are provided in the adjacent walls of the interfaced chambers. For example, transport modules are generally used in conjunction with a variety of substrate processing modules, which may include semiconductor etching systems, material deposition systems, and flat panel display etching systems. Due to the growing demands for cleanliness and high processing precision, there has been a growing need to reduce the amount of human interaction during and between processing steps. This need has been partially met with the implementation of vacuum transport modules which operate as an intermediate handling apparatus (typically maintained at a reduced pressure, e.g., vacuum conditions). By way of example, a vacuum transport module may be physically located between one or more clean room storage facilities where substrates are stored, and multiple substrate processing modules where the substrates are actually processed, e.g., etched or have deposition performed thereon. In this manner, when a substrate is required for processing, a robot arm located within the transport module may be employed to retrieve a selected substrate from storage and place it into one of the multiple processing modules.
As is well known to those skilled in the art, the arrangement of transport modules to "transport" substrates among multiple storage facilities and processing modules is frequently referred to as a "cluster tool architecture" system. FIG. 1A depicts a typical semiconductor process cluster architecture 100 illustrating the various chambers that interface with a vacuum transport module 106. Vacuum transport module 106 is shown coupled to three processing modules 108a-108c which may be individually optimized to perform various fabrication processes. By way of example, processing modules 108a-108c may be implemented to perform transformer coupled plasma (TCP) substrate etching, layer depositions, and/or sputtering.
Connected to vacuum transport module 106 is a load lock 104 that may be implemented to introduce substrates into vacuum transport module 106. Load lock 104 may be coupled to a clean room 102 where substrates are stored. In addition to being a retrieving and serving mechanism, load lock 104 also serves as a pressure-varying interface between vacuum transport module 106 and clean room 102. Therefore, vacuum transport module 106 may be kept at a constant pressure (e.g., vacuum), while clean room 102 is kept at atmospheric pressure. Consistent with the growing demands for cleanliness and high processing precision, the amount of human interaction during and between processing steps has been reduced by the use of robots 110 to transfer the wafers from the clean room 102 to the load lock 104.
FIG. 1B depicts a prior art robot 110 mounted along a track 112 between wafer cassettes 114 and two load locks 104 provided in the clean room 102. The clean room 102, with the cassettes 114 and the robot 110, is maintained at atmospheric pressure, thus these items may be referred to as parts of an atmospheric transfer module 116. The robot 110 can be moved transversely along the linear track 112 between ends 118a and 118b to facilitate removing a wafer 120 straight out of one of the cassettes 114. That is, during removal the wafer 120 must be aligned with a wafer transfer axis 122 that extends in the direction of a y-axis. The aligned transfer has been used to avoid difficulties experienced in the past in controlling robots during wafer transfer, e.g., when the base of the robot is rotated (theta motion) on a vertical axis at the same time as the arms of the robot are moved in an extend motion.
The load locks 104 are mounted opposite to the cassettes 114 and have front faces, or wafer transfer faces, 124 that are parallel to the track 112 and extend in the direction of an x-axis. Generally, there is a minimum distance (along the wafer transfer axis 122 of the load lock 104) required between the robot 110 (hence between the track 112) and the load lock 104 into which a wafer 120 is to be transferred. This minimum distance is the minimum distance required by the robot 110 to transfer a wafer 120 straight into the load lock port without rotation of the robot 110 on a robot central axis of rotation 126, and may be referred to as a wafer transfer distance, or wafer feed distance. The wafer feed distance is depicted by the dimension line 127 having opposite arrowheads and extending between the track 112 and the face 124 of the load lock 104. The wafer feed line, or dimension line, 127 is shown extending in the direction of the y-axis parallel to the wafer transfer axis 122, and both the line 127 and the axis 122 are perpendicular to the track 112 and to the y-axis.
The size of the robot track 112, and the need to lubricate the robot track 112, have caused problems in that the robot track 112 is relatively long in the direction of the y-axis. Also, lubrication on the track 112 is exposed, and is thus a "dirty" element in the otherwise "clean", clean room 102. Further, the length of the wafer transfer distance 127 must separate the robot 110, or the track 112, firm the face 124 of the load locks 104. In the past the length of the entire wafer feed distance, or dimension line, 127 extending in the direction of the y-axis has been between the track 112 and the face 124. A footprint of the combined atmospheric transfer module 116 and vacuum transfer module 106 is generally defined by the floor area occupied by these modules 106 and 116, such that the footprint is proportional to floor area dimensions along the x and y axes. Thus, the relatively long length of the track 112 in the direction of the x-axis, and the length of the entire wafer transfer distance 127 extending in the direction of the y axis, contribute to the size of the footprint of these modules 106 and 116. As shown in FIGS. 1B and 1C, in the direction of the y-axis, the length of a footprint dimension line 130 contributes to the size of the footprint. It is observed that the length of the entire wafer transfer distance 127 extending in the direction of the y-axis is part of the footprint dimension line 130, for example. In view of the increased cost of building and supporting clean run environments for such equipment, there is a great need to reduce the resulting footprint. In addition, if equipment footprint can be made smaller, production can be increased using the same amount of clean room space.
In view of the forgoing, what is needed is a robot that avoids the need for a track that is relatively long in the direction of the y-axis, and that does not present a track lubrication problem. Also, since there is a minimum length of the wafer transfer distance that must separate a robot from a wafer transfer face of a load lock, what is needed is a way of avoiding having that entire minimum length extend in the direction of the y-axis, such that the length of a footprint dimension line 130 extending in the direction of the y-axis, for example, does not include such entire minimum length. Further, in operations for transferring wafers into load locks, it should not be necessary to rotate the base of the robot on a vertical axis at the same time as the arms of the robot are moved in an extend motion.